Amidino derivatives and their use as nitric oxide synthase inhibitors

ABSTRACT

Amidino derivatives of formula (I) and salts, and pharmaceutically acceptable esters and amides thereof, in which: R 1  is a C 1-6  straight or branched chain alkyl group, a C 2-6  alkenyl group, a C 2-6  alkynyl group, a C 3-6  cycloalkyl group or a C 3-6  cycloalkylC 1-6  alkyl group; Q is an alkylene, alkenylene or alkynylene group having 3 to 6 carbon atoms and which may optionally be substituted by one or more C 1-3  alkyl groups; a group of formula --(CH 2 ) p  X(CH 2 ) q  -- where p is 2 or 3, q is 1 or 2 and X is S(O) x  where x is 0, 1 or 2, O or NR 2  where R 2  is H or C 1-6  alkyl; or a group of formula --(CH 2 ) r  A(CH 2 ) s  -- where r is 0, 1 or 2, s is 0, 1 or 2 and A is a 3 to 6 membered carbocyclic or heterocyclic ring which may optionally be substituted by one or more suitable substituents such as C 1-6  alkyl, C 1-6  alkoxy, hydroxy, halo, nitro, cyano, trifluoro C 1-6  alkyl, amino, C 1-6  alkylamino or diC 1-6  alkylamino; and pharmaceutical formulations containing them are described for use in medicine novel compounds of formula (I) and the preparation of such novel compounds are also disclosed.

The present invention relates to amidino derivatives, to methods fortheir manufacture, to pharmaceutical compositions containing them and totheir use in therapy, in particular their use as nitric oxide synthaseinhibitors.

It has been known since the early 1980's that the vascular relaxationbrought about by acetylcholine is dependent on the presence of theendothelium and this activity was ascribed to a labile humoral factortermed endothelium-derived relaxing factor (EDRF). The activity ofnitric oxide (NO) as a vasodilator has been known for well over 100years and NO is the active component of amylnitrite, glyceryltrinitriteand other nitrovasodilators. The recent identification of EDRF as NO hascoincided with the discovery of a biochemical pathway by which NO issynthesised from the amino-acid L-arginine by the enzyme NO synthase.

NO is the endogenous stimulator of the soluble guanylate cyclase and isinvolved in a number of biological actions in addition toendothelium-dependent relaxation including cytotoxicity of phagocyticcells and cell-to-cell communication in the central nervous system (seeMoncada et al, Biochemical Pharmacology, 38, 1709-1715 (1989) andMoncada et al, Pharmacological Reviews, 43, 109-142 (1991)). It is nowthought that excess NO production may be involved in a number ofconditions, particularly conditions which involve systemic hypotensionsuch as toxic shock and therapy with certain cytokines.

The synthesis of NO from L-arginine can be inhibited by the L-arginineanalogue L-N-monomethyl-arginine (L-NMMA) and the therapeutic use ofL-NMMA for the treatment of toxic shock and other types of systemichypotension has been proposed (WO 91/04024 and GB-A-2240041). Thetherapeutic use of certain other NO synthase inhibitors apart fromL-NMMA for the same purpose has also been proposed in WO 91/04024 and inEP-A-0446699.

It has recently become apparent that there are at least two types of NOsynthase as follows:

(i) a constitutive, Ca⁺⁺ /calmodulin dependent enzyme that releases NOfor response to receptor or physical stimulation.

(ii) a Ca⁺⁺ independent enzyme which is induced after activation ofvascular smooth muscle, macrophages, endothelial cells, and a number ofother cells by endotoxin and cytokines. Once expressed this inducible NOsynthase synthesises NO for long periods.

The NO released by the constitutive enzyme acts as a transductionmechanism underlying several physiological responses. The NO produced bythe inducible enzyme is as a cytotoxic molecule for tumour cells andinvading microorganisms. It also appears that the adverse effects ofexcess NO production, in particular pathological vasodilation and tissuedamage, may result largely from the effects of NO synthesised by theinducible NO synthase.

The NO synthase inhibitors proposed for therapeutic use so far, and inparticular L-NMMA, are non-selective in that they inhibit both theconstitutive and the inducible NO synthase. Use of such a non-selectiveNO synthase inhibitor requires that great care be taken in order toavoid the potentially serious consequences of over-inhibition of theconstitutive NO-synthase including hypotension and possible thrombosisand tissue damage. In particular, in the case of the therapeutic use ofL-NMMA for the treatment of toxic shock it has been recommended that thepatient must be subject to continuous blood pressure monitoringthroughout the treatment. Thus, whilst non-selective NO synthaseinhibitors have therapeutic utility provided that appropriateprecautions are taken, NO synthase inhibitors which are selective in thesense that they inhibit the inducible NO synthase to a considerablygreater extent than the constitutive NO synthase would be of evengreater therapeutic benefit and much easier to use.

The present invention concerns amidino derivatives of the formula (I)##STR2## and salts, and pharmaceutically acceptable esters and amidesthereof, in which:

R¹ is a C₁₋₆ straight or branched chain alkyl group, a C₂₋₆ alkenylgroup, a C₂₋₆ alkynyl group, a C₃₋₆ cycloalkyl group or a C₃₋₆cycloalkylC₁₋₆ alkyl group;

Q is an alkylene, alkenylene or alkynylene group having 3 to 6 carbonatoms and which may optionally be substituted by one or more C₁₋₃ alkylgroups;

a group of formula --(CH₂)_(p) X(CH₂)_(q) -- where p is 2 or 3, q is 1or 2 and X is S(O)_(x) where x is 0, 1 or 2, O or NR² where R² is H orC₁₋₆ alkyl; or

a group of formula --(CH₂)_(r) A(CH₂)_(s) -- where r is 0, 1 or 2, s is0, 1 or 2 and A is a 3 to 6 membered carbocyclic or heterocyclic ringwhich may optionally be substituted by one or more suitable substituentssuch as C₁₋₆ alkyl, C₁₋₆ alkoxy, hydroxy, halo, nitro, cyano,trifluoroC₁₋₆ alkyl, amino, C₁₋₆ alkylamino or diC₁ -alkylamino.

The compounds of formula (I) may include a number of asymmetric centresin the molecule depending on the precise meaning of the various groupsand formula (I) is intended to include all possible isomers. When thegroup Q is an alkenyl group such as --CH₂ CH═CHCH₂ --, both the E and Zisomers are included. The compounds of formula (I) all include anasymmetric centre in the group ##STR3## and although the natural L or(S) chirality of arginine is preferred, it is again intended that theformula should include all possible isomers.

The group A as a carbocyclic or heterocyclic ring may be saturated, mayinclude ethylenic unsaturation or may be aromatic. In the case of aheterocyclic ring the ring may contain one or more heteroatoms whichwill generally be selected from N, O and S.

Pharmaceutically acceptable esters and amides of the compounds offormula (I) may have the --CO₂ H end group replaced by --CO₂ R³ where R³is for example C₁₋₆ alkyl, aryl or arylC₁₋₃ alkyl or --COR⁴ where R⁴ isthe residue of a suitable natural of synthetic amino acid.

According to one aspect, the present invention provides the use of acompound of formula (I) as defined above or a pharmaceuticallyacceptable salt, ester or amide thereof for use in the manufacture of amedicament for the treatment of a condition where there is an advantagein inhibiting NO production from L-arginine by the action of NOsynthase.

According to a further aspect, the present invention provides a methodfor the treatment of a human or animal subject suffering from acondition where there is an advantage in inhibiting NO production fromL-arginine by the action of NO synthase which comprises administering tothe subject an effective amount to relieve said condition of a compoundof formula (I) as defined above or a pharmaceutically acceptable salt,ester or amides thereof.

The activity of a compound as an inhibitor of the enzyme NO synthase canbe determined by an assay in which a macrophage cell line (J774) isinduced to express NO synthase with lipopolysaccharide (LPS) andinterferon gamma and NO generated is measured by its reaction withhaemoglobin or as nitrite. This assay has the advantage of conveniencebut does not distinguish between selective and non-selective NO synthaseinhibitors. Selectivity can be determined by use of an assay based onrat aortic rings in vitro. The basal tone of the tissue is used as anindication of the activity of the constitutive NO synthase whereasLPS-induced loss of tone mediated by NO is used as an indication of theactivity of the inducible enzyme in the vascular smooth muscle cells.Selectivity can also be demonstrated by use of an assay based on themeasurement of rat blood pressure (constitutive enzyme) and rat bloodpressure in LPS treated rats (inducible enzyme). Compounds of formula(I) show activity as inhibitors of NO synthase in the J774 cell line anda number of compounds have also been demonstrated to be selectiveinhibitors in the rat aortic ring, in particular they have beendemonstrated to be some 10 to 40 times more potent as inhibitors of theinducible NO synthase than the constitutive NO synthase.

Conditions in which there is an advantage in inhibiting NO productionfrom L-arginine include systemic hypotension associated with septicand/or toxic shock induced by a wide variety of agents; therapy withcytokines such as TNF, IL-1 and IL-2; and as an adjuvant to short termimmunosuppression in transplant therapy.

There is also a growing body of evidence for the existence of a third NOsynthase enzyme which may be involved in the degeneration of cartilagewhich takes place in certain conditions such as arthritis and it is alsoknown that NO synthesis is increased in rheumatoid arthritis.Accordingly further conditions in which there is an advantage ininhibiting NO production from L-arginine include autoimmune and/orinflammatory conditions affecting the joints, for example arthritis.

As used herein, reference to "treatment" of a patient is intended toinclude prophylaxis.

Certain compounds of formula (I) are novel and according to a furtheraspect the invention provides amidino derivatives of the formula (IA)##STR4## and salts, and pharmaceutically acceptable esters and amidesthereof, in which:

R¹ is a C₁₋₆ straight or branched chain alkyl group, a C₂₋₆ alkenylgroup, a C₂₋₆ alkynyl group, a C₃₋₆ cycloalkyl group or a C₃₋₆cycloalkylC₁₋₆ alkyl group;

Q is an alkylene, alkenylene or alkynylene group having 3 to 6 carbonatoms and which may optionally be substituted by one or more C₁₋₃ alkylgroups;

a group of formula --(CH₂)_(p) X(CH₂)_(q) -- where p is 2 or 3, q is 1or 2 and X is S(O)_(x) where x is 0, 1 or 2, O or NR² where R² is H orCl₁₋₆ alkyl; or

a group of formula --(CH₂)_(r) A(CH₂)_(s) -- where r is 0, 1 or 2, s is0, 1 or 2 and A is a 3 to 6 membered carbocyclic or heterocyclic ringwhich may optionally be substituted by one or more suitable substituentssuch as C₁₋₆ alkyl, C₁₋₆ alkoxy, hydroxy, halo, nitro, cyano,trifluoroC₁₋₆ alkyl, amino, C₁₋₆ alkylamino or diC₁₋₆ alkylamino;

with the proviso that Q is neither CH₂ CH₂ CH₂ CH₂ nor CH₂ CH₂ CH₂ whenR¹ is methyl, or CH₂ CH₂ CH₂ when R¹ is ethyl.

According to another aspect, the present invention also providescompounds of formula (IA) as defined above and pharmaceuticallyacceptable salts, esters and amides thereof for use in therapy, inparticular the therapy of conditions where there is an advantage ininhibiting NO production from L-arginine by the action of NO synthase.

Specific examples of the group R¹ include methyl, ethyl, n-propyl,isopropyl, cyclopropyl, propenyl, n-butyl, t-butyl, cyclobutyl andcyclopropylmethyl.

Specific examples of the group A as a carbocyclic or heterocyclic ringinclude cyclohexyl, cyclopentyl cyclobutyl, cyclopropyl, cyclohexenyl,cyclopentenyl, cyclobutenyl, phenyl, pyridyl, piperidinyl, pyrrolyl,pyrrolidinyl, furanyl, tetrahydrofuranyl, thiazolyl, imidazolyl andoxazolyl. In each case the ring may optionally be substituted by one ormore suitable substituents such as the substituents mentioned above.

Particular examples of Q as an alkylene, alkenylene or alkynylene groupincludes groups of the formulae

--(CH₂)_(n) -- where n is 3 to 5;

--(CH₂)_(V) CH═CH(CH₂)_(w) ; and

--(CH₂)_(V) C.tbd.C(CH₂)_(w) ; where in each case v is 0 to 3 and w is 0to 3 with the proviso that the sum total of v+w is 2 to 4.

A preferred group of compounds of formula (I) are compounds in which:

R¹ is methyl;

Q is --(CH₂)_(n) -- where n is 3 to 5, more preferably 3 or 4;

--CH₂ CH═CHCH₂ --;

--(CH₂)_(p) X(CH₂)_(q) -- where p is 2 or 3, q is 1 or 2 and X isS(O)_(x) where x is 0, 1 or 2, more preferably 0, O or NR² where R² is Hor C₁₋₆ alkyl, more preferably C₁₋₃ alkyl; or

--(CH₂)_(r) A(CH₂)_(s) -- where r is 1 or 2, s is 1 or 2 and A is a 6membered carbocyclic or heterocyclic ring, more preferably one of thespecific rings referred to above, most preferably cyclobutyl, phenyl orpyridyl;

with the proviso that the group ##STR5## has the natural L or (S)chirality; and pharmaceutically acceptable salts, esters and amidesthereof.

A particularly preferred group of compounds of formula (I) are compoundsin which:

R¹ is methyl;

Q represents --(CH₂)_(n) -- where n is 3 or 4;

--CH₂ CH═CHCH₂ --;

--(CH₂)₂ SCH₂ --; or

--CH₂ ACH₂ -- where A is cyclopropyl;

and pharmaceutically acceptable salts, esters and amides thereof.

Specific preferred compounds of formula (I) are:

(S)-N⁵ -(1-iminoethyl)ornithine;

(S)-N⁶ -(1-iminoethyl)lysine;

(±)-E-2-amino-6-(1-iminoethylamino)-hex-4-enoic acid; and

(S)-S-2-(1-iminoethylamino)ethylcysteine and pharmaceutically acceptablesalts, esters and amides thereof.

The present invention includes compounds of formula (I) in the form ofsalts, in particular acid addition salts. Suitable salts include thoseformed with both organic and inorganic acids. Such acid addition saltswill normally be pharmaceutically acceptable although salts ofnon-pharmaceutically acceptable salts may be of utility in thepreparation and purification of the compound in question. Thus,preferred salts include those formed from hydrochloric, hydrobromic,sulphuric, citric, tartaric, phosphoric, lactic, pyruvic, acetic,succinic, oxalic, fumaric, maleic, oxaloacetic, methanesulphonic,ethanesulphonic, p-toluenesulphonic, benzenesulphonic and isethionicacids. Salts of the compounds of formula (I) can be made by reacting theappropriate compound in the form of the free base with the appropriateacid.

Whilst it may be possible for the compounds of formula (I) to beadministered as the raw chemical, it is preferable to present them as apharmaceutical formulation. According to a further aspect, the presentinvention provides a pharmaceutical formulation comprising a compound offormula (I) or (IA) or a pharmaceutically acceptable salt or solvatethereof, together with one or more pharmaceutically acceptable carrierstherefor and optionally one or more other therapeutic ingredients. Thecarrier(s) must be "acceptable" in the sense of being compatible withthe other ingredients of the formulation and not deleterious to therecipient thereof.

The formulations include those suitable for oral, parenteral (includingsubcutaneous, intradermal, intramuscular, intravenous andintraarticular), rectal and topical (including dermal, buccal,sublingual and intraocular) administration although the most suitableroute may depend upon for example the condition and disorder of therecipient. The formulations may conveniently be presented in unit dosageform and may be prepared by any of the methods well known in the art ofpharmacy. All methods include the step of bringing into association acompound of formula (I) or a pharmaceutically acceptable salt or solvatethereof ("active ingredient") with the carrier which constitutes one ormore accessory ingredients. In general the formulations are prepared byuniformly and intimately bringing into association the active ingredientwith liquid carriers or finely divided solid carriers or both and then,if necessary, shaping the product into the desired formulation.

Formulations of the present invention suitable for oral administrationmay be presented as discrete units such as capsules, cachets or tabletseach containing a predetermined amount of the active ingredient; as apowder or granules; as a solution or a suspension in an aqueous liquidor a non-aqueous liquid; or as an oil-in-water liquid emulsion or awater-in-oil liquid emulsion. The active ingredient may also bepresented as a bolus, electuary or paste.

A tablet may be made by compression or moulding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared bycompressing in a suitable machine the active ingredient in afree-flowing form such as a powder or granules, optionally mixed with abinder, lubricant, inert diluent, lubricating, surface active ordispersing agent. Moulded tablets may be made by moulding in a suitablemachine a mixture of the powdered compound moistened with an inertliquid diluent. The tablets may optionally be coated or scored and maybe formulated so as to provide slow or controlled release of the activeingredient therein.

Formulations for parenteral administration include aqueous andnon-aqueous sterile injection solutions which may contain anti-oxidants,buffers, bacteriostats and solutes which render the formulation isotonicwith the blood of the intended recipient; and aqueous and non-aqueoussterile suspensions which may include suspending agents and thickeningagents. The formulations may be presented in unit-dose or multi-dosecontainers, for example sealed ampoules and vials, and may be stored ina freeze-dried (lyophilised) condition requiring only the addition ofthe sterile liquid carrier, for example, saline, water-for-injection,immediately prior to use. Extemporaneous injection solutions andsuspensions may be prepared from sterile powders, granules and tabletsof the kind previously described.

Formulations for rectal administration may be presented as a suppositorywith the usual carriers such as cocoa butter or polyethylene glycol.

Formulations for topical administration in the mouth, for examplebuccally or sublingually, include lozenges comprising the activeingredient in a flavoured basis such as sucrose and acacia ortragacanth, and pastilles comprising the active ingredient in a basissuch as gelatin and glycerin or sucrose and acacia.

Preferred unit dosage formulations are those containing an effectivedose, as hereinbelow recited, or an appropriate fraction thereof, of theactive ingredient.

It should be understood that in addition to the ingredients particularlymentioned above, the formulations of this invention may include otheragents conventional in the art having regard to the type of formulationin question, for example those suitable for oral administration mayinclude flavouring agents.

The compounds of the invention may be administered orally or viainjection at a dose of from 0.1 to 500 mg/kg per day. The dose range foradult humans is generally from 5 mg to 35 g/day and preferably 5 mg to 2g/day. Tablets or other forms of presentation provided in discrete unitsmay conveniently contain an amount of compound of the invention which iseffective at such dosage or as a multiple of the same, for instance,units containing 5 mg to 500 mg, usually around 10 mg to 200 mg.

The compounds of formula (I) are preferably administered orally or byinjection (intravenous or subcutaneous). The precise amount of compoundadministered to a patient will be the responsibility of the attendantphysician. However the dose employed will depend on a number of factors,including the age and sex of the patient, the precise disorder beingtreated, and its severity. Also the route of administration may varydepending on the condition and its severity.

Compounds of formula (I) can be prepared by reaction of an amino acid offormula (II) ##STR6## or a protected derivative thereof, with a compoundof formula (III) ##STR7## where L is a leaving group and R¹ and Q are asdefined above, followed by removal of any protecting groups present.

Suitable leaving groups L include --OR⁵ and --SR⁵ where R⁵ is a loweralkyl group, e.g. C₁₋₄ alkyl, preferably methyl or ethyl.

The compound of formula (II) will generally be used in a form in whichthe amino acid functionality is protected by suitable protecting groupsand in this connection reference can be made to T. W. Greene and P. G.M. Wuts, Protective Groups in Organic Synthesis, 2nd Edition, John Wileyand Sons Inc., 1991. The protecting groups can then be removed inconventional manner (loc. cit.) as the final stage of the process toyield the compound of formula (I). For example the amino acidfunctionality can be protected as the copper salt with deprotectiontaking place on an ion exchange column which is employed to removeinorganic ions from the reaction mixture.

The compounds of formula (III) can be used in the form of the free baseor as an acid addition salt, e.g. the hydrochloride or hydroiodide salt.

The reaction is generally carried out in a suitable solvent in thepresence of base, e.g. an alkali metal hydroxide such as sodiumhydroxide, preferably at a pH of about 9 to 11 and generally at atemperature from 0° C. up to the reflux temperature of the solvent,preferably 0° C. to 50° C. The preferred solvent is water although thereaction may also be carried out in a polar solvent such as a loweralcohol, e.g. methanol or ethanol, or an amide, e.g. dimethylformamide,either alone or in admixture with water, and this may be advantageous incertain circumstances.

The compounds of formula (II) are in general known compounds which canbe converted into appropriate protected derivatives in known manner. Theimidates and thioimidates of formula (II) (L is --OR⁵ and --SR⁵respectively) are also in general known compounds and the reaction ofsuch compounds with a primary amine is discussed for example in TheChemistry of Amidines and Imidates, Vol. 2, Eds. Saul Patai and ZviRappaport, John Wiley and Sons Inc., 1991.

The invention is illustrated by the following Examples.

EXAMPLES Example 1 (S)-N⁵ -(1-Iminoethyl)ornithine hydrochloride

L-Ornithine hydrochloride (10.1 g, 60 mmol) was dissolved in hot-water(10 ml) and the solution was stirred at 100° during the portionwiseaddition of copper carbonate (7 g) over 15 minutes. The dark bluesolution was cooled to room temperature, filtered, and the residue waswashed with water (20 ml).

The combined filtrate and washings were stirred at 5° during theportionwise addition of ethyl acetimidate hydrochloride (11.1 g, 90mmol); throughout the addition the solution was maintained at a pH of10.5 by simultaneous addition of 2N aqueous sodium hydroxide. Thesolution was then allowed to stand at room temperature for one hour,acidified with 2N aqueous hydrochloride to pH3 and applied to a column(150 ml) of cation exchange resin Bio-Rad AG 50W-X8 (hydrogen form). Thecolumn was washed with water until the eluate was neutral and theneluted with 0.5N aqueous ammonia. The ninhydrin positive fractions werecombined and evaporated under reduced pressure at 40° C. for a shorttime to remove ammonia. The solution was then carefully acidified to pH4with 2N aqueous hydrochloric acid and evaporated to dryness underreduced pressure.

The residue was crystallised by dissolving in a little water, adding alarge volume of ethanol and allowing the mixture to stand at 40° for afew hours. The precipitate was filtered, washed with ethanol, and driedin a desiccator under reduced pressure to give the title compound as acolourless crystalline solid mp. 226°-228°.

Example 2 (S)-N⁶ -(1-Iminoethyl) lysine hydrochloride

Essentially by the methods of Example 1 L-lysine hydrochloride (7.3 g, 4mmol) was converted to the copper complex which was reacted with ethylacetimidate hydrochloride (7.5 g, 60 mmol). The title compound, isolatedas described in Example 1, was obtained as a hygroscopic amorphouspowder.

Example 3 (±)-E-2-Amino-6-(1-Iminoethylamino)-hex-4-enoic acidhydrochloride

The methods of Example 1 were used to convert E-4,5-dehydrolysinehydrochloride to the title compound which was obtained in an amorphousstate, homogenous by t.l.c. in a mixture of acetonitrile/water/aceticacid (5:3:2), and with n.m.r. spectrum (D₂ O) and mass spectrumconsistent with the proposed structure.

Example 4 (S)-S-2-(1-Iminoethylamino)ethylcysteine hydrochloride

Using the methods of Example 1 (S)-S-2-(1-aminoethylcysteinehydrochloride (2 g, 10 mmol) was converted to the copper complex, andreacted with ethyl acetimidate hydrochloride (1.88 g, 15 mmol). Theproduct was isolated as described in Example 1 to give the titlecompound as a pale yellow amorphous solid, homogeneous by t.l.c. in amixture of acetonitrile/water/acetic acid (5:3:2), and with n.m.r.spectrum (D₂ O) and mass spectrum consistent with the proposedstructure.

The compounds of Examples 5 to 11 were prepared, essentially by themethods of Example 1, by reaction of the copper complex of theappropriate amino acid of formula (II) with the relevant ethylalkanimidate hydrochloride.

Example 5 (S) -N⁶ -(1-Iminopropyl) lysine hydrochloride

The title compound was isolated as a hygroscopic amorphous white powder,homogeneous by t.l.c. in a mixture of acetonitrile/water/acetic acid(5:3:2).

Mass spectrum: (M+1)⁺,202.0.

Example 6 (S)-N⁶ -(α-Iminocyclopropylmethyl)lysine hydrochloride

The title compound was isolated as a hygroscopic amorphous white powder,homogeneous by t.l.c.

Mass spectrum: (M+1)⁺,214.0.

Example 7 (±)-2-Amino-7(1-iminoethylamino)-heptanoic acid hydrochloride

The title compound was obtained as amorphous material, homogeneous byt.l.c., in a mixture of acetonitrile/water/acetic acid (5:3:2).

Mass spectrum: (M+1)⁺,202.0.

¹ H-NMR (200 M-Hz, D₂ O): 1.22-1.43 (m, 2CH₂), 1.50-1.70 (m CH₂),1.75-1.90 (m, CH₂), 2.1 (s, CH₃), 3.10-3.20 (t, CH₂), 3.60-3.72 (t, CH).

Example 8 (±)-Z-2-Amino-6-(1-iminoethylamino)-hex-4-enoic acidhydrochloride

The title compound crystallised from a mixture of ethanol and water togive colourless crystals, mp. 223°-225°, homogeneous by t.l.c. in amixture of methanol/0.880 ammonia (7:3).

Mass spectrum: (M+1)⁺,186.0. ² H-NMR (200 M-Hz, D₂ O): 2.22 (s, CH₃),2.66-2.76 (m, CH₂), 3.80-3.90 (t, CH) 3.80-4.00 (d, CH₂), 5.70-5.80 (m,2 CH).

Example 9 (S) -N⁵ -(1-Iminoprop-1-yl) ornithine hydrochloride

The title compound was obtained as a pale yellow amorphous solid,homogeneous by t.l.c. in a mixture of acetonitrile/water/acetic acid(5:3:2).

Mass spectrum: (M+1)⁺,188.0. ² H-NMR (200 M-Hz, D₂ O): 1.05-1.08, (t,CH₃), 1.55-1.90 (m, 2CH₂), 2.30-2.45 (q, CH₂), 3.13-3.28 (t, CH₂),3.62-3.72 (t, CH).

Example 10 (S)-N⁵ -(1-Iminobut-2-yl) ornithine hydrochloride

The title compound crystallised from ethanol containing a trace of waterto give a crystalline solid mp. 202°, homogeneous by t.l.c., in amixture of acetonitrile/water/acetic acid (5:3:2). ¹ H-NMR (200 M-Hz, D₂O): 1.21-1.29, (d, 2CH₃), 1.61-1.85 (m, CH₂), 1.82-2.01 (m, CH₂)2.65-2.88, (s, CH), 3.25-3.39 (t, CH₂), 3.74-3.84 (t, CH).

Example 11 (S) -N⁵ -(α-Iminocyclopropylmethyl)ornithine hydrochloride

The title compound crystallised from a mixture of ethanol and water togive a colourless crystalline solid mp. 2.75°-2.77°, homogeneous byt.l.c., in a mixture of acetonitrile/water/acetic acid (5:3:2).

Mass spectrum: (M+1)⁺,200. ¹ H-NMR (200 M-H_(z), D₂ O): 1.0-1.30 (m,2CH₂), 1.60-2.05 (m, 2CH₂, CH), 3.25-3.40 (t, CH₂), 3.70-3.85 (t, CH).

Biological Data

The activity of certain compounds of formula (I) as NO synthaseinhibitors has been determined in the following assays:

Constitutive NO synthase--method of Rees et al, Br. J. Pharmacol., 101,746-752 (1990)

Inducible NO synthase--method essentially according to Rees et al,Biochem. Biophys. Res. Comm., 173, 541-547 (1990).

The results were as follows:

    ______________________________________              NO Synthase Activity    Compound of               Constitutive Inducible    Example No.               EC.sub.50 μM                            EC.sub.50 μM                                     EC.sub.50 ratio    ______________________________________    1          5.1          0.14     36.4    2          6.9          0.16     43.1    3          3.1          0.32     9.7    4          4.3          0.13     33.4    ______________________________________

We claim:
 1. A compound of the formula: ##STR8## wherein: R¹ is methyl;Q is --CH₂ CH═CHCH₂, --(CH₂)_(p) X(CH₂)_(q) -- where p is 2 or 3, q is 1or 2 and X is S(O)_(x) where x is 0, 1 or 2, O or NR² where R² is H orC₁₋₆ alkyl or --(CH₂)_(r) A(CH₂)_(s) -- where r is 1 or 2, s is 1 or 2and A is cyclobutyl, phenyl or pyridyl; with the proviso that the group##STR9## has the natural L chirality; or a pharmaceutically acceptablesalt, a pharmaceutically acceptable ester wherein --CO₂ H is replaced by--CO₂ R³, with R³ being selected from C₁₋₆ alkyl, aryl or aryl C₁₋₃alkyl, or a pharmaceutically acceptable amide thereof wherein --CO₂ H isselected with COR⁴ with R⁴ being an amino acid.
 2. A compound as claimedin claim 1 wherein x is 0 or R² is C₁₋₃ alkyl.
 3. A compound as of theformula: ##STR10## wherein: R¹ is methyl; Q is --CH₂ CH═CHCH₂ --,--(CH₂)₂ SCH₂ -- or --CH₂ ACH₂ -- where A is cyclopropyl; or apharmaceutically acceptable salt, a pharmaceutically acceptable esterwherein --CO₂ H is replaced by --CO₂ R³, with R³ being selected fromC₁₋₆ alkyl, aryl or aryl C₁₋₃ alkyl, or a pharmaceutically acceptableamide thereof wherein --CO₂ H is replaced with --COR⁴ with R⁴ being anamino acid.
 4. A method for the treatment of a human or animal subjectsuffering from a condition where therapeutic benefit is provided byselectively inhibiting NO production from L-arginine by the action ofinducible NO synthase which method comprises administering to thesubject an effective amount to relieve said condition of a compound ofclaim 1, 2 or
 3. 5. A method as claimed in claim 4 wherein the conditionis septic shock an autoimmune disease, an inflammatory condition orarthritis.
 6. A pharmaceutical composition comprising a compound asdefined in claim 1, 2 or 3 or a pharmaceutically acceptable saltthereof, together with one or more pharmaceutically acceptable carrierstherefor.